Regression testing for agent changes in Agentic AI

Introduction

Regression testing helps make sure that when you change an AI agent, it still works well and does not break old features.

After updating the AI agent's code or logic

When adding new skills or tasks to the agent

Before releasing a new version of the agent

To check if bug fixes did not cause new problems

When changing the environment or data the agent uses

Syntax

Agentic AI

def regression_test(agent, test_cases):
    results = {}
    for name, input_data, expected_output in test_cases:
        output = agent.run(input_data)
        results[name] = (output == expected_output)
    return results

This function runs a list of test cases on the agent and checks if outputs match expected results.

Each test case has a name, input, and expected output to compare.

Examples

This example tests if the agent responds correctly to greetings and farewells.

Agentic AI

test_cases = [
    ('greet_test', 'Hello', 'Hi! How can I help?'),
    ('farewell_test', 'Bye', 'Goodbye!')
]
results = regression_test(agent, test_cases)

Here, the agent is tested on math and weather questions to check consistency.

Agentic AI

test_cases = [
    ('math_test', '2 + 2', '4'),
    ('weather_test', 'Weather today?', 'Sunny')
]
results = regression_test(agent, test_cases)

Sample Model

This program defines a simple agent and runs regression tests to check if it responds correctly to different inputs.

Agentic AI

class SimpleAgent:
    def run(self, input_text):
        if input_text == 'Hello':
            return 'Hi! How can I help?'
        elif input_text == 'Bye':
            return 'Goodbye!'
        else:
            return 'I do not understand.'

def regression_test(agent, test_cases):
    results = {}
    for name, input_data, expected_output in test_cases:
        output = agent.run(input_data)
        results[name] = (output == expected_output)
    return results

agent = SimpleAgent()
test_cases = [
    ('greet_test', 'Hello', 'Hi! How can I help?'),
    ('farewell_test', 'Bye', 'Goodbye!'),
    ('unknown_test', 'What?', 'I do not understand.')
]
results = regression_test(agent, test_cases)
print(results)

Important Notes

Always keep your test cases updated when you add new features.

Regression tests help catch bugs early before users see them.

Automate regression testing to save time and avoid mistakes.

Summary

Regression testing checks if agent changes break old behavior.

Use test cases with inputs and expected outputs to verify the agent.

Run regression tests regularly to keep your agent reliable.

Practice

1. What is the main purpose of regression testing for agent changes?

easy

A. To check if new changes break old agent behavior

B. To improve the agent's speed

C. To add new features to the agent

D. To change the agent's user interface

Solution

1. Step 1: Understand regression testing goal

   Regression testing is done to ensure that recent changes do not break existing functionality.

2. Step 2: Match purpose with options

   To check if new changes break old agent behavior clearly states checking if new changes break old behavior, which matches the goal.

3. Final Answer:

   To check if new changes break old agent behavior -> Option A

4. Quick Check:

   Regression testing = check old behavior intact [OK]

Hint: Regression testing checks old features still work after changes [OK]

Common Mistakes:

• Thinking regression testing adds new features
• Confusing regression testing with performance testing
• Assuming regression testing changes UI

2. Which of the following is the correct way to define a test case for regression testing an agent in Python?

easy

A. def test_agent(): assert agent.run(input) == expected_output

B. test agent run input equals expected output

C. def test_agent: return agent.run(input) == expected_output

D. function test_agent() { return agent.run(input) == expected_output; }

Solution

1. Step 1: Identify correct Python function syntax

   Python functions start with 'def', have parentheses, and a colon.

2. Step 2: Check assertion usage

   def test_agent(): assert agent.run(input) == expected_output uses 'assert' correctly to compare output, matching Python test style.

3. Final Answer:

   def test_agent(): assert agent.run(input) == expected_output -> Option A

4. Quick Check:

   Python test function with assert = def test_agent(): assert agent.run(input) == expected_output [OK]

Hint: Python test functions start with def and use assert [OK]

Common Mistakes:

• Missing parentheses or colon in function definition
• Using non-Python syntax
• Not using assert for test checks

3. Given the code below, what will be the output of the regression test?

class Agent:
    def run(self, x):
        return x * 2

def test_agent():
    agent = Agent()
    result = agent.run(3)
    assert result == 6
    print('Test passed')

test_agent()

medium

A. SyntaxError

B. Test passed

C. AssertionError

D. No output

Solution

1. Step 1: Understand agent run method

   The method multiplies input by 2, so run(3) returns 6.

2. Step 2: Check assertion and print

   The assertion checks if result == 6, which is true, so no error occurs and 'Test passed' prints.

3. Final Answer:

   Test passed -> Option B

4. Quick Check:

   3 * 2 = 6, assertion true, prints message [OK]

Hint: Check method output matches assertion to predict test result [OK]

Common Mistakes:

• Assuming assertion fails without checking output
• Confusing syntax errors with logic errors
• Ignoring print statement after assertion

4. Identify the error in the following regression test code and select the fix:

def test_agent():
    agent = Agent()
    result = agent.run(5)
    if result = 10:
        print('Test passed')
    else:
        print('Test failed')

medium

A. Replace print with return statements

B. Add parentheses around the if condition

C. Change '=' to '==' in the if condition

D. Remove else block

Solution

1. Step 1: Identify syntax error in if condition

   The single '=' is an assignment, not a comparison, causing a syntax error.

2. Step 2: Correct the comparison operator

   Replace '=' with '==' to compare values properly in the if statement.

3. Final Answer:

   Change '=' to '==' in the if condition -> Option C

4. Quick Check:

   Use '==' for comparison in if statements [OK]

Hint: Use '==' to compare, '=' assigns values [OK]

Common Mistakes:

• Using '=' instead of '==' in conditions
• Adding unnecessary parentheses in Python if
• Thinking print must be replaced with return

5. You updated your agent's decision logic. How should you design regression tests to ensure old behaviors remain correct while testing new features?

hard

A. Test randomly without expected outputs to save time

B. Only test new features since old ones worked before

C. Remove old tests to avoid conflicts with new logic

D. Create test cases for both old expected outputs and new expected outputs

Solution

1. Step 1: Understand regression test purpose

   Regression tests verify that old behaviors still work after changes.

2. Step 2: Design tests covering old and new behaviors

   Include test cases for old expected outputs and new expected outputs to check both.

3. Final Answer:

   Create test cases for both old expected outputs and new expected outputs -> Option D

4. Quick Check:

   Test old and new outputs to ensure full correctness [OK]

Hint: Test old and new cases to catch breaks early [OK]

Common Mistakes:

• Ignoring old tests after updates
• Deleting old tests to simplify
• Skipping expected outputs in tests